1. Field of the Invention
The present invention relates to selective termination of messaging operations in a unified messaging system configured for receiving incoming calls as voice message calls or incoming fax calls.
2. Description of the Related Art
The evolution of the public switched telephone network has resulted in a variety of voice applications and services that can be provided to individual subscribers and business subscribers. Such services include voice messaging systems that enable landline or wireless subscribers to record, playback, and forward voice mail messages. However, the ability to provide enhanced services to subscribers of the public switched telephone network is directly affected by the limitations of the public switched telephone network. In particular, the public switched telephone network operates according to a protocol that is specifically designed for the transport of voice signals; hence any modifications necessary to provide enhanced services can only be done by switch vendors that have sufficient know-how of the existing public switched telephone network infrastructure. Hence, the reliance on proprietary protocols and closed development environments by telecommunications equipment providers has limited service providers to vendor-specific implementations of voice and telephony services.
Voice over IP technology is under development as part of an alternative open packet telephony communications network, distinct from the public (circuit switched) telephone network, capable of using packet switched networks for integrating voice, data, facsimile, and Internet services, and the like. New packet telephony voice services are being built from open standards such as The International Telecommunications Union (ITU) Recommendation H.323. Recommendation H.323 defines the components, procedures, and protocols necessary to provide audiovisual communications on local area networks. Recommendation H.323 is based on the Real Time Protocol/Control Protocol (RTP/RTCP) of the Internet Engineering Task Force (IETF), and applies to either point-to-point or multipoint sessions, and references many other ITU recommendations, including H.225 and H.245. Recommendation H.225 specifies messages for call control including signaling, registration and admissions, and packetization/synchronization of media streams. Recommendation H.245 specifies messages for opening and closing channels for media streams, and other commands, requests and indications.
One problem encountered with unified messaging is the inability of a messaging application to distinguish between an incoming voice call and an incoming facsimile call for a unified messaging subscriber before initiating a voice messaging session. For example a gateway such as the Cisco AS5300 Universal Access Server, configured for receiving incoming calls (e.g., according to voice over IP protocol), may send a request to an application server to initiate a voice messaging session based on the assumption that the incoming call is from a calling party desiring to leave a voice message; however if the incoming call is from a fax machine, the gateway may not detect the facsimile machine tones for up to seven seconds after detecting the incoming call. Hence, different error conditions may occur if the fax machine interacts with the voice messaging session executed by the application server, depending on the programming of the voice messaging session: for example, the application server executing the voice messaging session could store the fax tones as a recorded message; the incoming fax call also could adversely affect the status of stored new messages if the messaging application is configured for message autoplayback, where new messages are played during the incoming fax call and redesignated as stored messages, adding further inconvenience to the messaging subscriber.
Hence, a gateway is unable to effectively distinguish between an incoming voice call and a fax call before sending a request to the application server to initiate the voice messaging session. In addition, delaying initiation of the voice messaging session while the gateway determines whether the incoming call is a fax call is not an acceptable alternative, since the calling party would then need to wait an unacceptably long interval before leaving a voice message. Hence, developers of messaging applications may be reluctant to provide advanced features due to concerns of an incoming fax call adversely affecting a messaging application. Limiting incoming fax calls to prescribed telephone numbers configured for connecting the incoming fax calls to a fax server also requires the use of multiple telephone numbers for a single subscriber, and limits the flexibility of unified messaging for a messaging subscriber.